Acrylic elastomeric materials and process therefor



United States Patent 3,502,745 ACRYLIC ELASTOMERIC MATERIALS AND PROCESSTHEREFOR Robert G. Minton, Levittown, Pa., assignor to Rohm & HaasCompany, Philadelphia, Pa., a corporation of Delaware No Drawing. FiledOct. 7, 1965, Ser. No. 493,922 Int. Cl. C08f /16, 15/40 US. Cl. 260-87817 Claims ABSTRACT OF THE DISCLOSURE Shaped polymer structures includingfibers and films are produced by means of a sequential polymerizationreaction wherein an elastomeric monomer mixture, such as a soft acrylicpolymer, having a second order transition temperature of 0 C. or less ispolymerized in a polymer latex of a highly crosslinked hard orreinforcing loader polymer having a second order transition temperatureof at least about 20 C. and a fine particle size of about 1 micron orless. Fibers spun from a latex of the sequential copolymer are stretchcured and are characterized by substantially improved tensile strength,equilibrium modulus and return modulus.

This invention relates to novel acrylic elastomeric materials; to shapedstructures, particularly films and threads prepared therefrom; and tothe methods of preparing such materials and the shaped products thereof.

The elastic properties of resins prepared from certain acrylic esters asethyl acrylate, butyl acrylate and 2- ethylhexyl acrylate have long beenknown. Such acrylic elastomers are particularly noted forheat-resistance, flex life and resistance to oil. Accordingly, severalacrylic elastomers are used commercially as the material of choice inapplication such as gaskets for automatic transmissions for gasolineengines wherein these outstanding properties are particularly desirable.However, acrylic elastomers are also characterized by poor tensilestrength and poor return modulus. Accordingly, wider application ofthese elastomers particularly in shaped structures such as threads andfilms has been limited.

Considerable work has been carried out to reinforce acrylic elastomersby suitable means. In particular, workers have sought to improve thestrength of acrylate elastomers by loading the elastomers withfinely-divided fillers, including amorphous silica and certain polyalkylmethacrylates, particularly polyme'thyl methacrylate and polyethylmethacrylate prepared in latex form and mixed with a latex of theelastomer. Some improvement in strength has been observed as a result ofthis technique.

However, the resulting compositions exhibit high set, loss ofrubberiness and a tensile strength still definitely J below that ofcompetitive elastomeric products, such as natural rubber.

It has now been found that synthetic elastomeric materials prepared by asequential polymerization process produce elastomeric products combiningthe known properties of acrylate elastomers with the high tensilestrength and return modulus of natural rubber.

In accordance with the invention, a latex is prepared of very small,crosslinked polymeric particles using a free radical catalyst. Theparticles of this latex act as a reinforcing polymeric material in thefinal composition. The monomer or monomers used in preparing the latexcomprise up to 99% of one or more vinylidene monomers which contain nohalogen as part of the vinylidene radical with one or more diorpoly-functional monomer (called the cross-linker) copolymerizable withthe vinylidene monomer(s) and effective to cross-link the resultingcopolymer. Suitable cross-linkers include monomers having 3,502,745Patented Mar. 24, 1970 at least two vinyl groups of sufiicientreactivity to allow independent copolymerization with the vinylidenemonomer(s) and monomers having only one vinyl group copolymerizable withthe vinylidene monomer(s) and one or more groups effective to cross-linkthe copolymer by means of a reaction which is triggered, i.e.,initiated, separately from the polymerization reaction. The crosslinkermust be present in sufficient amount to make the resulting copolymersubstantially insoluble in solvents for the polyvinylidene monomer(s).In some highly efiicient systems, as styrene-divinylbenzene, as littleas 0.1% of divinylbenzene based on the weight of the copolymer may beused. The maximum amount of cross-linker that may be used is notcritical. By means of cost it is generally preferred to use no more thanabout 25% of cross-linker based on the weight of the copolymer, althoughmore may be used if desired so long as a stable, fine-particle sizeemulsion is obtained. The vinylidene monomer(s) are selected so that thepolymer of such monomer(s) would itself (i.e., exclusive of thecross-linker) have a second order transition temperature of at least 20C.

After the preparation of the latex of the reinforcing polymeric material(termed the loader), there is then polymerized in the presence of thelatex and under conditions designed to minimize the formation of newparticles an elastomeric monomer mixture comprising (a) at least oneC2-C10 alkyl ester of acrylic acid or a mixture of one or more suchesters with up to an equal weight percent of ethylene, propylene and/ orisobutylene, and, (b) from about 0.5% to 25% by weight of the elastomerof at least one ethylenically unsaturated monomer copolymerizable withthe elastomer and effective to cross-link the elastomer by means of areaction which is triggered separately from the polymerization reaction(the combination of these monomers and, optionally, the hardener asdiscussed hereafter, is termed the elastomer mixture). Generally, thecross-linking reaction used to cross-link the elastomer mixture will bea condensation reaction. The monomers of the elastomer mixture must beso select ed that a polymer constituting the mixture has a second ordertransition temperature of no more than 0 C. and preferably of no morethan -20 C. The elastomer mixture constitutes from 35% to by weight ofthe total elastomeric composition while the loader representscorrespondingly from 65% to 10% by weight of the total composition. Thelatex obtained after polymerization of the elastomer mixture in thepresence of the loader is termed the elastomer latex.

The art of emulsion polymerization is Well-known and the conditions ofpolymerization used herein are not critical so long as a fine particledispersion is obtained for the loader. The latexes may be made using oneor more emulsifiers of anionic, cationic or non-ionic type. Mixtures oftwo or more emulsifiers regardless of type may be used, excepting thatit is generally undesirable to mix a cationic with an anionic type,since they tend to neutralize each other. By proper selection of theemulsifier, it is possible to obtain fine particle size and assure astable emulsion for the second sequential polymerization using less than1% by weight of the latex of the emulsifier. For most emulsifiersystems, it is preferred to use at least about 4% by Weight of the latexof the emulsifier. The polymerization may be initiated at a loweremulsifier con tent with incremental addition of the remainingemulsifier as polymerization proceeds. When using a persulfate type ofinitiator, lower amounts of emulsifier may be used since the initiatoritself has an emulsifying capability. The maximum amount of emulsifieris not critical and is generally determined by economic considerations.Generally no more than about 8% by weight of the total monomer chargewill be used. The latex so prepared should have an average particle sizeof no more than about 1 micron 3 in diameter and, preferably, from about60 to 400 millimicrons in diameter.

The free radical catalysts may be either water-soluble or oil-soluble.The invention contemplates the use of any of the free radical catalystsknown to the art as efliective to catalyze the polymerization of themonomers used herein. Particularly preferred are the peroxy catalystsand the azo-type catalysts. Typical catalysts which may be used areperoxides, such as hydrogen peroxide, dibutyl peroxide, acetyl peroxide,benzoyl peroxide; alkyl percarbonates; hydroperoxides, such ast-butylhydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide,etc.; perborates as the alkali metal and ammonium perborates;persulfates as the alkali metal and ammonium persulfates; etc. Othercatalysts such as (1,0;-azodiisobutyronitrile, diazoaminobenzene, etc.can be used. The quantity of catalyst used can be varied depending onthe monomer, the temperatures and the method of addition. Generally,from about 0.001 to 5% by weight, based on the weight of the monomers,is used. If desired, the catalyst may be omitted and ultravioletradiation used for the polymerization.

The catalyst may be used with a redox system. A buffer may be used foreither or both stages of the polymerization. The catalyst, emulsifierand monomer charge may all be added initially or one or more may beadded incrementally as polymerization proceeds. One type of catalystand/or emulsifier may be used in the polymerization of the loader and adifferent catalyst and/or emulsifier used for the subsequentpolymerization thereon of the elastomer mixture, or the same catalystand/or emulsifier may be used for both polymerizations, as desired.

The temperature of polymerization is not critical and may be varied atthe choice of the operator. Where a temperature below 0 C. is used, afreezing point depressant, as ethylene glycol, should be added to thewater. When the polymerization is run at the boiling point of themixture, reflux means should be provided. The polymerization may beconducted at atmospheric pressure or with the application of highpressures in which case temperatures exceeding the reflux temperature ofthe reaction mixture may be used. Optimum polymerization times will varyinter alia with the nature of the catalyst and the monomers, with thetemperature and pressure and with the degree of completeness to which itis desired to carry the polymerization.

Diand polyvinyl cross-linkers suitable for use in preparing the loaderinclude, for example, alkyleneor alkylidene-bis-acrylamides such asmethylene-bis-acrylamide, divinylbenzene, trivinylbenzene, divinylethers, divinyl sulfone, diallyl glycerol, glycerol trimethacrylate,triallyl cyanurate, tetraallyl melamine, hexaallyl melamine,tetraethyleneglycol, dimethacrylate, triacrylylperhydrotriazine,diallyladipate (or sebacate or maleate or fumarate) allyl acrylate,ethylene diacrylate, polyalkylene glycol diacrylate, diallylbenzenephosphonate, diethylene-glycolbis-allyl-carbonate,2,4-diallyloxy-6-amino-5-triazine, butylene diacrylate, ethylenedimethacrylate, vinyl 4-pentenoate, etc. A mixture of cross-linkers maybe used. The other group of cross-linkers which may be used, i.e.monomers with only one vinyl group together with one or more groupseffective to cross-link the copolymer by means of a reaction which istriggered separately from the polymerization reaction, are, in general,the same cross-linkers used in the elastomer mixture as describedhereinafter with the exception that the cross-linking reaction mustproceed inside the individual latex particles under conditions which donot break the emulsion.

Other monomers which may be copolymerized with the cross-linker toprovide up to 99% of the loader include, for example, methylmethacrylate, ethyl methacrylate, t-butyl acrylate, styrene,ot-methylstyrene, acrylonitrile, vinyl pyridine, vinyl toluene, etc. Inaddition, monomers whose homopolymers have a second order transitiontemperature below 20 C, such as la ryl m th.-

acrylate, may be included so long as the other monomers present otherthan the cross-linker are such as to give a copolymer having a secondorder transition temperature of at least 20 C. Because of their thermalstability, acrylate and methacrylate monomers are particularly preferredfor the loader. The loader may also contain one or more monomers whichcan undergo a condensation reaction with one or more complementarymonomers in the clastomer mixture.

After preparation of the loader latex, the monomers in the elastomermixture are added to the latex and polymerized therein. If desired,additional emulsifier and/or catalyst may be added for the secondpolymerization.

It is believed that some type of chemical bonding occurs between theelastomer and the particles of the reinforcing polymeric latex. When theloader and the elastomer mixture contain complementary monomers whichcondense with each other, such bonding is accentuated. Even in theabsence of such complementary monomers some type of bonding is believedto occur. The precise nature of the reactions occurring in thesequential polymerization used to produce the novel copolymers of theinvention is not known.

The term rubbery monomer is somewhat inapposite as applied to monomersin that it is the polymer which is rubbery. However, with thisqualification, the term rubbery monomer is used herein to designatethose monomer or monomers responsible for the elasticity, that is, therubberiness of the final product. The rubbery monomers used in theinstant invention are alkyl esters of acrylic acid having from 2 to 10carbon atoms in the alkyl chain or mixtures of one or more of suchesters with each other or with up to an equal weight of ethylene,propylene and/or isobutylene which monomer or monomer mixtures produce arubbery, non-crystalline polymer or copolymer. Moreover, the polymerproduced from the monomer mixture constituting the complete elastomermixture (i.e., the rubbery monomer or monomers, the cross-linker andwhere appropriate, the hardener) must have a second order transitiontemperature of no more than 0 C. and preferably no more than 20 C.Preferred rubbery monomers include ethyl acrylate, propyl acrylate,butyl acrylate, 2-ethylhexyl acrylate, a mixture of ethyl acrylate withfrom about 20-30% by weight of the mixture of ethylene, etc.

If desired, a small portion of the acrylate monomer constituting theprincipal component of the elastomer mixture may be replaced by asuitable monomer copolymerizable therewith and which does not interferewith the elasticity thereof. Generally, such monomers are themselvesacrylates or methacrylates whose homopolymers display some elasticity.Thus, if desired, a minor amount, say about 5% by weight of theprincipal alkyl acrylate, may be replaced with methyl acrylate or2-ethylhexyl methacrylate, etc. without departing from the invention.

Optionally, the elastomer mixture contains one or morea,/8-monoethylenically unsaturated monomers which are effective toincrease the second order transition temperature of the copolymer. (Forthe method of determining the second order transition temperature of apolymer, see D. G. Bannerman and E. E. Magat, page 288 in PolymerProcesses, C. E. Schildknecht, ed., Interscence Publishers Inc., 1956.)Monomers having this effect on the copolymer are termed hardeners. Anymonomer whose homopolymer is hard and non-elastic at 50 C. may be used.Thus, those monomers are included whose homopolymers are highlycrystalline and possess a high melting point, such as polyvinylidenechloride, and also those monomers whose homopolymers possess a highsecond order transition temperature. Suitable hardeners includevinylidene chloride, vinyl chloride, acrylonitrile, vinyl pyridine,methacrylonitrile, methyl methacrylate, styrene, vinyl toluene, ethylmethacrylate, acrylic acid, methacrylic acid and itaconic acid.Acrylonitrile is particularly preferred as a hardener for butyl acrylateand for 2-ethylhexyl acrylate.

Many of the monomers useful as cross-linkers for the acrylic elastomerare also highly effective as hardeners. According to one embodiment ofthe invention, such monomers are used in preparing the elastomericccopolymers in amounts greatly in excess of that needed to achievecross-linking. The cross-linking reaction is then controlled so thatonly a portion of the available crosslinking monomer units are utilizedfor such cross-linking, the portion of the monomer units not utilized inthe cross-linking being retained in the polymer to function as ahardener. In addition to acting as hardeners, such residual monomerunits may also improve dyeing and, in some cases, increase the stabilityof the resulting sequential copolymers. Further, where the novel latexof the invention is used in a coating composition, such monomer unitsmay improve the adhesion of the coatings to a variety of substrates.

The amount of hardener which may be used in the elastomer mixture willvary with the nature of the hardener or hardeners, the rubbery monomeror monomers, and on the properties desired in the product. In any event,the total of the non-rubbery monomers present in the elastomer mixturemust be such that the polymer produced from the mixture does not have asecond order transition temperature of more than C. and preferably ofnot more than 20 C. Generally, the hardener should not constitute overabout 20% by weight of the elastomer mixture and preferably not overabout 15%. A hardener is particularly desirable with butyl acrylate andZ-ethylhexyl acrylate, whereas no hardener is generally needed withethyl acrylate. In a preferred embodiment, non-acidic hardeners asacrylonitrile, vinylidene chloride or methyl methacrylate are used withone or more acidic hardeners as acrylic acid, methacrylic acid oritaconic acid to give the desired total hardener content.

The monomers used to cross-link the elastomeric c0- polymers comprisefrom about 0.5 to 25% by weight of the copolymer although it is believedthat no more than about by weight of the elastomeric copolymer is usedin the cross-linking reaction. For applications requiring highextensibility, as in elastic fibers, less than 1% by weight of themonomers in the elastomeric copolymer is believed to be used in thecross-linking reaction. The use of excess amounts of the cross-linkingmonomer (i.e. greater than about 5%) in the elastomer mixture issometimes advantageous, however, in making possible more rapid curing,in providing reactive groups in the resulting product which improve thedye receptivity and other properties of the polymer, and to act ashardeners as described above. Preferably, the cross-linker monomer unitscomprise no more than about 5% by weight of the elastomer mixture. Whenthe cross-linker constitutes more than about 5% by weight of theelastomer mixture, care must be taken during curing to prevent excessivecrosslinking which would be detrimental to the elasticity of thecopolymers.

The monomers effective as cross-linkers in the elastomer mixture (and,optionally, in the loader) are unsaturated monomers copolymerizable withthe alkyl acrylates and containing one or more reactive groups whosereactivity is triggered separately from the polymerization reaction. Apreferred class of such reactive groups are those which are capable ofundergoing a condensation reaction such as amide, alcoholic hydroxyl,amino, carboxylic acid, ure-ido, epoxy, etc.

Another type of monomer that may be used as a crosslinker in theelastomer mixture is one that contains one (and only one) unsaturatedcarbon-to-carbon linkageof sufficient reactivity to allowcopolymerization with the other m0nomer(s) in the elastomer mixture andone or more additional unsaturated carbon-to-carbon linkages which areof too low a reactivity to undergo such copolymerization. When acopolymer is formed using such a monomer, the unsaturated linkages oflow reactivity will be attached to the polymer chain as pendant groups,i.e., they will not be part of the polymer chain itself. Such pendantunsaturated linkages of low reactivity may be used to cross-link thepolymer chains as by a vulcanizing process using sulfur, dicumylperoxide or resin cures. Such processes are particularly applicable tosheet stock and to molding compositions. Examples of such crosslinkersare vinyl crotonate and 2-butenyl methacrylate. Wi'h the exception ofthis type of cross-linker (i.e. one giving only pendant unsaturatedlinkages in the copolymer), all other monomers used as cross-linkers inthe elastomer mix are monoethylenically unsaturated.

Examples of monomers that may be used to provide reactive groups thatcan undergo a condensation reaction include the following:

FOR ALCOHOLIC HYDROXYL Hydroxyalkyl vinyl ethers or sulfides in whichthe hydroxyalkyl group contains 1 to 3 hydroxyl groups and 2 to 18carbon atoms, such as ,B-hydroxyethyl vinyl ether, fl-hydroxyethyl vinylsulfide, S-hydroxypentyl vinyl sulfide, and l8-hydroxyoctadecyl vinylsulfide.

A hydroxyl-containing ester of an nap-monoethylenically unsaturated acidin which the. hydroxy group may be in the acid or the alcoholic moietyof the ester or both such moieties may contain hydroxyl. The unsaturatedacid from which the ester is derived may be monocarboxylic orpolycarboxylic. Examples include acrylic, methacrylic, itaconic, maleic,fumaric, crontonic, a-hydroxyalkyl-acrylic, aconitic, citraconic,wacryloxyacetic, and tit-methacryloxypropionic. Representative estersare 2-hydroxyethyl acrylate or methacrylate, methyla-(hydroxyme-thynacrylate, ethyl ot-(hydroxymethyl)-acrylate, butyltil-(2- hydroxyethyl)-acrylate, 2-hydroxypropyl acrylate ormethacrylate, 3-hydroxypropyl acrylate or methacrylate, methyla-(2-hydroxypropyl)-acrylate, ethyl u-(3-hydroxypropyl)-acrylate,4-hydroxybutyl acrylate or methacrylate, IO-hydroxydecyl acrylate ormethacrylate, the corresponding hydroxyalkyl crotonates,di(2-hydroxyethyl)-maleate or fumarate, di(10-hydroxydecyl) maleate orfumarate, the corresponding itaconates, mixed esters of dibasic acidscontaining a single hydroxy group as monohydroxyethyl-monomethylmaleate, and the like. Additionally, other substituents may beincorporated into the alkyl chain, including secondary hydroxy groups,halide radicals, nitrile radicals, and the like, such as 2,3-dihydroxypropyl acrylate, 3,5-dihydroxyamyl crontonate.6,10-dihydroxydecyl methacrylate, di-2,6-dihydroxyhexyl maleate, anddi-2-chloro-7-hydroxyheptyl fumarate. In all cases, the hydroxyl of eachhydroxyalkyl group is at least two carbon atoms removed from the carbonatom of the adjacent o J-O radical in the ester. Vinyl esters of hydroxyacids, as vinyl lactate and glycollate, can also be used to supplyhydroxy functionality.

FOR AMIDES Compounds of the formula:

H2C C(CH2)nlH N-alkoxymethyl or N-acyloxymethyl as above defined.

Also compounds of the formula:

wherein n, R and R are as above defined.

Examples of suitable amides include acrylarnide, methacrylamide,N-methylol-acrylamide, N-methoxymethylmethacrylamide, Nbutoxymethylacrylamide, N-fi-hyciroxyethylacrylamide, Nmethylacrylamide, 4-pentenamide, N-methylol-4-pentenamide,N-acetoxymethylacrylamide, and N-benzylacrylamide. Amides and imides ofdibasic unsaturated acids may also be used.

FOR UREIDO Compounds of the formula:

H C=C(R)ZA N(R )CXNR R wherein R is selected from the group consistingof H, alkyl groups having 1 to 4 carbon atoms, hydroxyalkyl groupshaving 1 to 4 carbon atoms, and alkoxymethyl groups having 2 to 5 carbonatoms,

A is an alkylene group having 2 to 8 carbon atoms, Z is O, S,

R is H or methyl,

R and R are as defined hereinbefore, and

X is selected from the group consisting of oxygen and sulfur.

wherein X is as defined above and A is an alkylene group having 2 to 3carbon atoms. One of the nitrogen atoms is connected to a polymerizablemonoethylenically unsaturated radical and the substituent on the othernitrogen may simply be hydrogen, or it may be methylol, alkoxymethylhaving 2 to 5 carbon atoms, hydroxyalkyl having 2 to 4 carbon atoms oran aminoalkyl group having 2 to 8 carbon atoms.

The preferred cyclic ureido compounds are those which contain the group:

HzC-GH:

Which may be termed the cyclic N,N-ethyleneureido group.

Many monoethylenically unsaturated monomers contain cyclic ureido groupsand are useful as cross-linkers for carrying out the invention.Compounds of the follow= ing formulas wherein Y represents the group ofthe formula above and R is H, methylol or methoxymethyl,

is preferably H, are typical:

wherein X and A are as defined hereinabove;

H2o=o R) o Z AYR wherein Z is selected from the group consisting of -Oand NR R being selected from the group consisting of H, cyclohexyl,benzyl, and an alkyl group having 1 to 6 carbon atoms, and A and R areas defined hereinabove; i HZC=C(R)CNROHZYR4 Wherein R is H or alkyl of 10t 12 carbon atoms, and R, Y and R are as defined hereinabove;

wherein R, R, R, Y and A are as defined hereinabove. Also included areacids in which the nitrogen atom of maleamic acid, chloromaleamic acid,fumaramic acid, itaconamic acid, or citraconamic acid is substituted by,and directly connected to a group of the formula:

wherein A, X and R are as defined hereinabove.

The N -substituted amic acid and esters derived from maleamic acid aretypical and have the following generic formula:

0 II X wherein A, X, R and R are as defined hereinabove.

The internai cyclic imides derived from maleamic acid have the formula:

Other such monomers have the following formula:

where A and R are as defined hereinahove and one R may be the same ordifferent than the other;

The unsaturated diearboxylic acid monoesters of a compound of theformula:

HOA1(OA)HN NR4 wherein A 11, A and R are as defined hereiobefore,derived from maleic, fumaric, chloromaleic, itaconic or citraconie acid.

9 FOR EPOXY Any monoethylenically unsaturated monomer containing aglycidyl radical may be used. Preferred monomers are glycidyl acrylate,glycidyl methacrylate, the acrylate and methacrylate esters of3-hydroxymethyl, 3-methyl oxetane, and the vinyl ethers and sulfidescontaining a glycidyl radical described by Murdoch and Schneider in US.Patent 2,949,474.

FOR CARBOXYLIC ACID Any or,fi-monoethylenically unsaturatedmonocarboxylic or dicarboxylic acid may be used. Examples are acrylicacid, methacrylic acid, maleic acid, fumaric acid, itaconic acid,citraconic acid, mesaconic acid, etc. Monoesters of the dibasic acidsmay also be used, as monomethyl maleate, monobutyl itaconate, etc. Theanhydrides, as maleic anhydride, may be used, though generallyhydrolysis occurs in the emulsion leading to formation of the free acid.

Other condensation-type cross-linking systems may be used such asmethoxymethyl vinyl sulfide, 2-aminoethyl methacrylate, etc.

These monomers may be used alone or in combination. Suitablecombinations of reactive cross-linking monomers result in a copolymerwhich is self-curing; that is, the two types of reactive groups presentin the copolymer react with each other to cure the copolymer. Thus,methacrylamide, acrylamide, and/or 4-pentenamide with one or more of thecorresponding N-methylol derivatives; hydroxyethyl acrylate withitaconic acid; glycidyl methacrylate with methacrylic acid and/orhydroxypropyl methacrylate; etc., are examples of such combinations ofcrosslinking monomers. If desired, a single cross-linking monomer may beused which requires that the copolymer be treated with an additionalchemical reagent to effect cure. Thus, when an amide, as acrylamide,and/or methacrylamide is used as the sole crosslinking agent, thepolymer must be treated with a chemical such as glyoxal,a-hydroxyadipaldehyde, other dialdehydes, formaldehyde or aformaldehyde-yielding material during the cross-linking operation.Formaldehyde-containing polymer-forming materials such asphenol-formaldehyde, urea-formaldehydo or melamine-formaldehydecondensates may also be used. Where the elastomeric composition isformed into sheets or molding compositions, the cross-linker can be achlorine-containing monomer or a carboxylic acid-containing monomer. Inthe first case, an amine and a basic divalent metal compound (as 2110)are added to the finished polymer, while in the second case divalentmetal ions or an epoxy resin or diepoxide are used to treat the polymer.A single monomer which is self-condensing may also be used, such as theN-methylol derivatives of acrylamide, methacrylate, 4-pentenamide, etc.Combinations of the same type of reactive monomer may also be used.Thus, N-methylol methacrylamide and N-methylol- 4-pentenamide may beused, or glycidyl methacrylate with hydroxypropyl methacrylate andmethacrylic acid, or N- methylolacrylamide with N-acetoxyacrylarnide, orhydroxyethyl methacrylate with methacrylic acid and itaconic acid, etc.Generally, the cross-linking reaction is triggered by heating theelastomeric composition, generally in the presence of a suitablecatalyst. If desired, a photosensitizing compound may be added to anelastomeric composition containing a suitable cross-linker and thecross-linking reaction triggered by irradiation from a suitable lightsource.

After completion of the two polymerization steps, if it is desired toform fibers, the elastomer latex is then spun, coagulated and cured.Spinning and coagulation are carried out in a single step. The processof emulsion spinning is described in US. Patent Nos. 2,869,977; 2,914,-376; and 2,972,511 and the disclosures of these patents are incorporatedherein. While the selection of a specific spinning process will dependupon the nature of the emulthereby eliminating any problem fromundesirable residues, it is preferred to use hydrochloric acid for thebath. For this acid, the coagulating bath should contain from about 9%to 37% hydrochloric acid by weight. If de sired, a salt as sodium orzinc chloride can be added to the acidic bath to assist the coagulatingaction. Although the formation of fibers and/or films according to theinvention will be described in terms of an acidic coagulating bath, itis understood that the process is not limited thereto, and eitheralkaline or all salt systems may be used as disclosed in the above-citedpatents.

While it is preferred to spin the emulsions into a coagulating bath asdescribed, the emulsions may also be dry-spun as described in BritishPatent 853,483. In dryspinning, it is preferred to extrude the fibersonto a heated adhesive support as a steel belt coated withpolytetrafiuoroethylene.

The elastomeric materials of the invention need no fusion aid norplasticizer nor heating step to promote fusion of the particles in aseparate fusion step. Thus, the elastomer latex of the invention issimilar to natural rubber latex in this regard. The spinning andcoagulating bath is maintained at a temperature between about 0 and C.and preferably between about 15 and 80 C. The higher preferredtemperature gives best results for high molecular weight latexes, whilefor lower molecular weight latexes the preferred temperature should notbe over about 40 C. At higher temperatures, the uncured fiber or film istoo weak to handle easily while at the lower temperatures coagulatingproceeds very slowly.

On leaving the spinning and coagulating bath, the fiber or film iswashed. The washing need not be carried out to remove all traces of acidremaining, as such traces serve to catalyze many of the condensationreactions used in cross-linking the elastomeric chains. Where theelastomeric copolymer contains free carboxylic acid units in the polymerchain (as by inclusion in the hardener or cross-linker), such acidicunits occurring in the chain serve as a built-in catalyst to promote thecondensation step. Thus, it is not essential in the instant invention toretain a trace amount of the acid from the coagulating bath.

Curing is accomplished by heating the fiber or film in the presence of acatalyst (the nature of the catalyst being determined by thecross-linking reaction, though generally acid catalysts are used) at atemperature from about 75 to C. for from about three hours to a fewseconds, the longer time corresponding to the lower temperature and theshorter time of cure corresponding to the upper temperature. The precisetime and temperature will depend upon the properties desired in thefinal product, the nature of the monomers, the necessity of avoiding theevolution of steam at a rate which would create bubbles in the fiber, onthe number and type of crosslinking monomer units in the elastomer andon the concentration and nature of the catalysts provided for the curingstep. In a preferred embodiment of the invention, the fiber or film iscured while held in the stretched condition.

The curing may be carried out in steps. Thus, the fiber or film may bepartially cured to increase the strength of the fiber or film to permiteasier handling of the material during the stretching and final cureoperations. The partial curing appears important to obtain the optimumresults from a final stretch-cure, though this need not be carried outas a separate step but may be the initial part of a continuous cureprocess. Stretch-curing achieves a certain minimum stabilization oforientation in the elastomer chains, which assists the action of theloader in improving tensile strength and modulus. As the conditions ofcuring tend to cause disorientation, it is evident that to obtain thebest properties for a particular use from a given system requirescareful control of the pre-cure, stretching and final cure. Adequatepartial curing may be achieved in from 30 minutes to 0.1 minute or lessat a temperature of from about 75 C. to about 150 C. Again, the longertime is used for the lower temperature, while a shorter time is used forthe higher temperature. Air-drying of the fiber at room temperatureachieves adequate partial curing though longer times are necessary.Preferably the partial curing is accomplished in a few seconds to fiveminutes at a temperature of 75 to 120 C. The fiber or film is thenstretched about 100% to 800% or higher and, while held in the stretchedcondition, the cure is completed.

Jet-stretching, i.e., stretching by pulling the fiber away from thespinning jet, appears to change only denier and may be used to stretchthe fiber any desired amount, i.e., more than 800%, to obtain thedesired denier. Again, the final cure may be carried out in about threehours to seconds at 75 to 180 C. (all temperatures specified in thisdiscussion of curing refer to the temperature of the medium surroundingthe fibers, which temperature is not necessarily the temperature of thefibers or film). Where the polymer is to be processed in fiber form, thefinal stretch-curing operation may be carried out by wind ing the fiberon a bobbin under a sufficient tension to impart the desired degree ofstretch and the curing carried out on the bobbin.

As will be obvious to those skilled in the art, a great variety ofstretching operations may be used. Thus, the wash bath may be maintainedat the temperature necessary to effect cure and the stretching carriedout in the wash bath. The fibers or films may also be stretched directlywhile drawn from the coagulating bath onto the drying rolls. Or again,precuring may be effected in the wash bath and the stretch accomplishedWhile drawn onto the drying rolls. Curing may take place on the dryingrolls or while being drawn through a steam chamber. The stretchingoperation includes, optionally, a low temperature or fast stretch. Thestretch-curing significantly increases the tensile strength and modulusof the resulting products Without adversely affecting the otherdesirable properties of the materials. The ability to stretch-orient theelastomeric materials of the invention even though they contain anon-crystalline filler is highly unusual and unexpected. It is believedthat this is due to the us of the cross-linking mechanism in twoseparate stages resulting in what can be called a two-network matrix.

The elastomer latexes produced by the invention may be spun through asingle filament jet to produce a monofil. Monofils of large diameter maybe produced by spinning about to 100 or more separate filaments in amultifilament jet and coalescing the separate filaments to form a singlelarge denier filament. Thus, filaments of from about 10 to 3000 deniermay be produced as desired. The latex may also be spun through amultifilament jet to produce a multifilament tow. The fiber may bechopped up into staple in which form it may be blended with non-elasticstaple fibers (both natural and synthetic) and spun or may be used witha binder either alone or in combination with other fibers to producenon-woven fabrics.

The elastomeric fibers produced according to the invention have physicalproperties far superior to those heretofore obtainable with acrylicrubbers and equaling or surpassing natural rubber and spandex fibers inmany properties. At the same time, While possessing vastly improvedphysical properties, the acrylic elastomeric fibers of the inventionretain the premium properties of stability, color, etc. associated withthe acrylic elastomers. As a result of their excellent physicalproperties, fibers of the acrylic elastomers of the invention may beused in any of the applications heretofore associated with naturalrubber or spandex fibers.

Thus, the fibers of the invention are useful in Weaving and knittinggenerally; in producing tricot knits and leno weaves; and in producingcovered fibers as those described in U.S. Patent Nos. 3,038,295 or3,011,302. The fibers may also be used in producing a plied fiber asdescribed in U.S. application Ser. No. 293,661, filed on July 9, 1963 byM. Storti, and in U.S. application Ser. No. 316,601, filed Oct. 16, 1963by M. ,Storti. These processes for covering or plying an elastic yarnwith a nonelastic fiber restrict the maximum elongation of the compositefiber. Most commercial applications of elastic yarns require only low ormedium elongation of the fiber. Thus, bathing suits are customarily madeof yarn having an elongation in the range of to The knitting tradegenerally requires yarns having an elongation from about to 200%, whilethe weaving trade (broadloom) generally requires yarns having anelongation of only from about 100% to 140%. The hosiery trade requiresyarn with an elongation of from 300% to 400%. The elastic fibers of theinvention are suitable for use in most of these commercial applicationsof elastic yarn. While it is preferred to produce fibers directly byspinning the latex as described, it is understood that the latex may becompounded and sheeted out and used to produce cut thread.

While the novel polymers have been described principally in fabricatingfibers and films, they have a variety of other useful applications.Thus, they may be used as protective coatings for wood, metal, etc.; inelastic foams; for dolls faces, dental dams; coatings for paper,leather, textiles, etc.; gaskets; as an adhesive particularly fortextiles as in flocking, laminating, etc.; mechanical goods; binders fornon-woven textiles; and other applications Where rubber latexes havebeen found useful.

In these applications the careful control of stretching and curingessential to produce optimum properties in fibers and films areunnecessary. Thus, the latex is treated like a conventional rubber latexin being coagulated, washed, compounded with various additives onsuitable mixing equipment and either sheeted out or used as a moldingcomposition. The excellent tensile strength and elasticity of theproducts of the invention coupled with their superior resistance tosolvents, chlorine and peroxide bleaches, ultraviolet, etc. characterizethese products as superior materials for such uses.

The polymeric compositions of the invention are highly desirable forproducing foams characterized by resilience, compression strength andoutstanding whiteness stability. Such foams may be subjected to drycleaning or washing with regular household detergents and bleacheswithout yellowing or other noticeable degradation. The foams are highlyresistant to ultraviolet radiation. Thus, the foams are eminentlysuitable for use as fabric liners, cosmetic foams, cigarette filters,air and/ or oil filters, cushion filler, insulation, etc. Depending onthe end use, the foams may be closed-cell or open-cell. Any of theprocesses customarily used in foaming latexes may be used, e.g. thosedescribed in U.S. patent application Ser. No. 350,676 filed on Mar. 10,1964 by Gill et al. For foam applications it is preferred to use a latexwhich has amide-methylolamide cross-linking groups in the rubber phaseand to blend an aminoplast, as a methylated melamine-formaldehyde resin,with the latex to assist the cross-linking reaction. Such combinationshave outstanding scorch resistance.

The elastomer latexes of the invention are also useful in transfercoating applications such as those described in U.S. patent applicationsSer. No. 390,059 filed on Aug. 17, 1964 by Storti and Ser. No. 390,669filed on Aug. 19, 1964 by Scofield. Again, for this application it ispreferred to use a latex which has amide-methylolamide cross-linkinggroups in the rubber phase and to blend an aminoplast as a methylatedmelamine-formaldehyde resin, with the latex to assist the cross-linkingreaction. Desirably, maleic acid or ammonium thiocyanate is used ascatalyst, as described in U.S. patent application Ser. No. 473,198 filedon July 19,1965 by Shelley. As in the case of the compositions describedby Shelley, coatings of the latex cast on a suitable adhesive surfaceare stable B-stage materials highly suitable for laminating operationsas described by Shelley, Storti and Scofield.

The resistance of the polymers of the mventionto sunlight and otherefiects of weather make them particularly To assist those skilled in theart to practice the present invention, the following modes of operationare suggested by way of illustration. All parts are by weight unlessotherwise stated.

suitable for impregnating cloth to produce novel rubbercoated fabricssuitable for rain gear, tents, tarpaulrns, etc. EXAMPLES 1 To 4 In thisapplication. as in i and transfi-er coatmg apgh- First a latex of theloader polymer is prepared To cations, modulus is less important than1r;J fibersd softdgt 200 g d ed W r re ad 4 gra s Ofthe use billklerrubbery i f t rubber sodium salt of an alkylaryl polyether sulfonate(27% slred, and, In any a hlgher g 2: EL; s: solids) and 100 grams of amonomer mixture. The ma- Phase iff :5 i i gz i z: a1 one or as a copolyterials are charged to a flask equipped with a reflux contlons' t bWeight of ethylene is denser, stirrer and thermometer. A nitrogenatmosphere mer wllth the ruber ymonomofls) In gem is maintained in theflask and stirring is commenced and Pamcu ar y use as y fi Se continuedthrough the reaction. A solution is prepared era], the rubbery Phaseprovlqes an 1 l y a u th of 0.04 gram of ammonium persulfate dissolvedin 4 m1. perature and sufi'icient loader is used to ensure that e ofwater. Heat is pp o t e sk and hen the Composition is non'tacky use fi itemperature reached 70 C. half of the ammonium perg lf y ggfi i g as aat ener o sulfate solution is added. Heating is continued until thelmpart i i g g z hvin one ver thin beginning of reflux and then isadjusted to maintain a F ucmg S ape S g th gentle reflux. After theinitial part of the polymerization, dlmenslon as fibers or films It Ispreferred to use e the remainder of the ammonium persulfate solution isrubbery molnomer l g gg gfgg zi z s added and heating at reflux iscontinued for one hour. n'butyl or mm was 9 e The contents of the flaskare allowed to cool and are then acrylates with each other or with up toan equal Weight filtered through acheesecloth amount of ethylene. ASecond fl ask e m ed as abov ha d Tenslle Strengths 0f fiber Samples fdeterinmed 132.5 g. of the late)? s produced this l atgx zifitaihi rigon i igzg Tester and are measured m pounds per 40 g. of polymer solids,200 gms. of deionized water, 90.0 q e 1 g. of butyl acrylate, -8.0 ofacr lonitrile, 0.8 of acr l- Elongation as used 1n the examples meanselongation amide and 12 gof Nfnethylolyacrylamide ,f p yg at h break ItIS measurled by placmg bench marks two en'zation is conducted exactly asfor the first latex using centimeters apart on a uniformly cut sampleand stretchan additional 4 m1. of 1% by Weight ammonium P it until itbreaks The percent.elongailon i l the (113' sulfate solution added intwo equal increments The tance,between the marks at fallum mmus dwldedby 2 stirrer speed is adjusted as the polymerization proceeds and times100. as necessary to maintain the dispersion.

Set is the unrecovered stretch after an elastomer 1s The latex soproduced is extruded through a 12 mil stretched and allowed to relaxfreely. It is determined by IJ1 glass capillary immersed i a b thontaining conpla'cing bench marks on the samp 1e cemlmeters. apartcentrated hydrochloric acid The fiber thus formed is and stretching it300% and holding for ten minutes. uned from the bath contin'uousl b aodet d1 Where the sample is stretched more or less than 300%, 40 aSheets of o1 tetrafluoroeth g g E t i i the amount of stretch isspecifically indicated. The sample h y h 1 y S c is released andmeasured after ten minutes. Set is recorded 3 t 65 are t i P acfad f twommutes a as the length of the sample at the 10-minute measurement,clrculatmg f oven Whlch mamtams an oven tempera minus 2 divided by 2 andtimes ture of 120 C. to pre-cure the samples. The samples are Returnmodulus is the stress on the return cycle ft then cured an add tional 58minutes in the crrculatlng air a strain larger than that at the measuredpoint has Oven 100 Table I Sets forfh the moffomer been imposed. Indetermining return modulus, the sample COHIPOSIUQII 1n the loader andthe P y Propeftles of is placed in the Instron Tester, elongated to apoint bethe fibers so produced. All of these fibers contain 40 parts lowthe breaking elongation, the crosshead returned to of loader per hundredparts of the elastomer mixture the rest position and cycled in thismanner for six cycles. (i.e., phr).

TABLE I EMA/DVB* Return (parts: Tensile Elongation 300% Mod. Mod.150/300 Runn. Set Ex. parts) (p.s.i.) (percent) (p.s.i (p.s.i.)(percent) EMA is ethyl methacrylate and DVB is divinylbenzene.

A similar elastomer latex prepared without any crosslinker in theloader, i.e., the loader consisted of 100% polyethyl methacrylateproduced films which were relatively stiff and nonrubbery.

EXAMPLES 5 TO 10 A series of six elastomer latexes are made and spuninto fibers as in Examples 1 to 4 using for the loader the loader ofExample 4 and using as the elastomer'mixture 90 grams of butyl acrylate,8,grams of acrylonitrile, 0.8 gram of methacrylamide, and 1.2 grams ofmethylol methacrylamide. In each example, different amounts of loaderare added per 100 parts of the elastomer mixture. Table II sets forththe amount er loader per 100 parts of elastomer mixture and theproperties of the fibers prepared from the resulting elastomer latex.z:

spinning of the elastomer latex into fibers are carried out as inExamples 1 to 4 except that no heat applied to the polymerization flask;the monomers used in the loader are varied; in Examples 25 and 30, 0.5g. of pentaer'ythritol tetrakisthioglycolate is added as apolymerization modifier; and in Examples 25 to 27 and 30 to 32, theemulsifier consisted of a mixture of 3 grams of the alkylaryl polyethersulfonate (27% solids) used in Examples 1 to 4 and 3 e TABLE II eStretch 5 r 300% RIlIlIlset" Loadin cure Elong. Tensile Modulus Ret.Mod. percent/ Ex (phr (percent) (percent) (p.s.i.) (p.s.i.) (150/300)300 Return modulus s 40 100 30s 2 000 32 41 18 i 9 50 100 285 3, 510 8210---... 60 100 260 610 60 110 e EXAMPLES" 11 TO 22 A series of twelve eastomer latexes are prepared and spun into fibers as in Examples 1 to*4. In each case, the leader of Example 4 is used. In Examples 11 to 13and 17 to 19, the elastomer mixture is 98 g. of combined butyl acrylateand acrylonitrile, 0. 8 g. of acrylamide and 1.2 g. ofmethylolacrylamide while in the remaining examples the elastomer mixtureis 98 g. of combined butyl acrylate and acrylonitrile, 0.8 g. ofmethacrylamide and 1.2 g. of methylolmethacrylamide. In each case 40parts oi loader are used per 100 parts elastomer mixture. The amounts ofbutyl acrylate and acrylqnitrile and the properties of the fibers soproduced are set forth in TableiII: t

parts of the sodium salt of a branched alkyl sulfate (25 solids) inplace of the 5 grams of the sodium alkylaryl polyether sulfonate= In allthe examples, the polymerization of the elastomer mixture is elfectuatedby charging the polymerization vessel described in Examples 1 to 4 with1325 grams of the loader latex (containing 40 g. polymer solids), 200parts of water butferedby a mixture of HCl and KCl to a pH of 2.5, 90grams of butyl acrylate, 8 grams of acrylonitrile, 0.8 gram ofmethacrylamide and 1.2 grams of N-methylolmethacrylamide. The system waspurged with nitrogen for 30 minutes and then 1 of a 10% ammoniumpersulfate solution and 1 ml. of a 10% solution of sodium thiosulfateare added and the nitrogen purge'continued. The polymerizationisallowed'to run TABLE III Stretch Return Runn. cure Elong. Tensilemodulus Set percent BA/AN (percent) (percent) (p.s.i.) (150/300) (300)00/8 0 575 2, 170 28 1 7 85/13 0 408 2, 570 a 'i 35 80/ 18 0 390 3, 040V 90/8 0 415 2, 300 42 38 85/13 0 350 g 2, 910 40 45 /18 0 340 3, 540 5860 50/200 100/200 Percent 200 EXAMPLES 23 TO 32 In the following tenexamples, a series of elastomer latexes are prepared. The preparation ofuntil conversion reached 97-99% The stirrer speed is kept at a leveljust sufficient to maintain the monomer disthe loader and the 75 pereed.The composition of the monomers used in prepar- 17' ing the loader andthe properties of the fibers produced are set forth in Table IV:v

sisting of 98 g. of ethyl acrylate, 0.8 g. methacrylamide and 1.2 g.methylolmethacrylamide polymerized on 40 TABLE IV Return Modulus StretchRunn. Set

Cure Elong. Tensile 80/200 100/200 (perccnt/ Ex. Loader (percent)(percent) (p.s.i.) (p.s.i.) 200) 23 EMA/DVB (98/2) 265 24.- MA/DVB 0 35625.- EMA/DVB (98/2) 0 300 26 MMA/B GDM (98/2) 0 336 2 MMA/V-4-P (95/5).0 325 2 EMA/DVB (98/2) 200 195 29- EMA/DVB (98/2) 200 290 30 EMA/DVB(98/2) 200 227 31.-.- MMA/B GDM (98/2). 200 228 32 MMA/V4-P (95/5) 200250 3,900 42 130 22 B GDM-1,3-butylene glycol dimethacrylate. MMAmethylmethacrylate. V4Pvinyl-4-pentenoate.

EXAMPLES 33 TO 36 parts of the loader as above using the method ofExamples A series of four elastomer latexes are prepared and spun 2023-32 for Examples 37 and 38 and the method of Exinto fibers. Theprocedure for preparing the loaders is as set forth in Examples 1 to 4except that the monomers used for the loader in Examples 33 and 34consisted of 95 parts amples 3336 for Examples 39 and 40. The resultingelastomer latexes are spun as in Examples 1 to 4. The properties of thefibers so produced are set forth in Table VI:

TABLE VI Runn. Stretch Return Modulus Set Cure Elong. Tensile (percent/Ex (percent) (percent) (p.s.i.) 50/200 100/200 200) styrene and 5 partsdivinylbenzene, while in Examples 35 EXAMPLES 41 TO 43 and'36 themonomers used consisted of 95 parts butyl methacrylate and 5 partsdivinylbenzene. The elastomer mixture described in Examples 5 to 10 ispolymerized on the loader latex parts by weight of loader per 1 00 partsof elastomer mixture), using the process described in Examples 23 to 32,except that deionized water is used in place of buffered Water and 2 ml.of a fresh 2% Formopon solution is substituted for the sodiumthiosulfate solution. The spinning process described in Examples 1 to 4is used. The properties of the fibers so prepared are set forth in TableV:

TABLE V reproduced, this example having the same chemical com- Retummodulus position as in Example 42 but prepared by a sequential Stretchpolymerization process, i.e., the elastomer latex is a chemi- E .335?33.31? (p.s.i.) 5 cal mixture rather than a mechanical mixture of theloader 0 324 2 430 28 68 with the elastomer mixture. In each case, theelastomer 100 207 I 35 92 latexes so produced are spun into fibers as inExamples 1 0 320 2.140 33 77 to 4. The properties of the fibers soprepared are set forth 100 300 1,900 35 in Table VII:

TABLE VII 7 Runn. Stretch Return Modulus Set 5 Cure Elong. Tensile(percentl. Ex. (percent) (percent) (p.s.i.) 50/200 100/200 200) A series.of three elastomer latexes are prepared and spun into fibers. InExample 41, the elastomer latex consists of parts butyl acrylate, 8parts acrylonitrile, 0.8 part methacrylamide and 1.2 part methylolmethacrylamide, i.e., no loader is used in this elastomer latex. Thepolymerization is carried out as described in Examples 33 to 36. InExample 42, 1 00 parts of the elastomer latex prepared in Example 41 aremechanically mixed with 40 parts of a separately prepared loader, theloader in this case bein the loader prepared in Example 27.

Finally, for Example 43, the data of Example 27 are The return modulusfor Example 42 is 35 at 200/400.

I EXAMPLES 37 TO 40 A series of four elastomer latexes are prepared andspun into fibers. In Examples 37 and 38, the loader is prepared asdescribed in Examples 1 to 4 using the monomer mixture of Example 4except that 0.5 g. of pentaerythritol tetrakisthioglycolate is added asa polymerization modifier. In Examples 39 and 40 the loader consisted ofg. of styrene and 5 g. of divinylbenzene. The elastomer latex isprepared using parts of an elastomer mixture con- 75 methacrylamide and1.2 parts methylolmethacrylamide;

EXAMPLES 44 AND 45 The elastomer latexes are prepared usingthe'procedure 70 described in Examples 23 to 32 and are spun into fibersas described in Examples 1 to 4. In each case, the loaderconsists of 38parts methyl methacrylate and 2 parts mers of Example 47 in the presenceof the loader latex of Example 48, i.e., sequentially.

TABLE VIII Runn. Stretch Return Modulus Set Cure Elong. Tensile(percent/ Ex. (percent) (percent) (p.s.i.) 50/200 100/200 200) EXAMPLE46 Five moles of formaldehyde per mole of amide is added Using theprocedure of Examples 1 to 4, a loader latex is prepared consisting of90 parts methyl methacrylate and 10 parts vinyl-4-pentenoate. Thepolymerization vessel described in Examples L4 is charged with 132.5parts (containing 40 parts of polymer) of this loader latex which hasbeen stripped of residual monomer. To the latex is added 30 parts of amonomer mixture consisting of 89.3 parts of butyl acrylate, 8 parts ofacrylonitrile, 0.7 part of Z-methyl-S-vinyl pyridine and 2.0 parts ofmethacrylamide. A subsurface nitrogen sparge is started and continuedfor 30 minutes. At this point, 1.5 parts of a solution of 0.2 part ofammonium persulfate (APS) in 9.8 parts of water is added followed after2 minutes by 0.6 part of a solution of 0.2 part of Formopon (sodiumformaldehyde sulfoxylate) in 9.8 parts of water. A mild exotherm occursand after it levels out, the remaining 70 parts of monomer mix, whichhas been emulsified in 50 parts of water with 4 parts of an aqueoussolution of the sodium salt of an alkylaryl polyether sulfonate (28%solids) and sparked with nitrogen, is added over a period'of 1.5 hours.At the mid-point of this addition, an additional 1.5 parts of APSsolution and 0.6 part of Formopon solution are added. This is repeated/2 hour after the addition is complete and after an additional threehours the emulsion is filtered through cheesecloth. The yield of polymeris 9699% of theory.

To 200 parts of the above latex is added 0.8 part of a solution of 10parts of the sodium salt of formaldehydecondensed naphthalene sulfonicacid in 90 parts of water and 6.7 parts of 37% formaldehyde. This isallowed to age for 48 hours and 5 parts of a dispersion of rutiletitanium dioxide prepared by mixing 200 parts of TiO 4 parts sodiumformaldehyde naphthalene sulfonate, 0.1 part of the benzyl ether of analkylaryl polyether ethanol and 296 parts of water in a high speed mixerare added. The resulting mixture is extruded through a 20 ml. I.D. glasscapillary immersed in a concentrated hydrochloric acid bath; The fiberproduced is carried out of the bath over a godet, washed in a flowingwater bath by wrapping on a set of canted rolls which are partiallyimmersed in the water, dried and cured on heating, canted rolls held at140 C. The fiber is then passed over a roll which has a thin coating ofan emulsion of 7 parts of 50 centistoke silicone oil in 93 parts ofcombined water and emulsifier and is finally wound up on a bobbin.

' Theproduct fiber has a tensile strength of 3600 p.s.i., an elongationof 400%, is white, and may be dyed with either acid dyes or neutralmetallized dyes.

EXAMPLES 47 TO 49 A series of three elastomer latexes are prepared andspun into' fiber. In Example 47, the elastomer latex consists of 90parts butyl acrylate, 8 parts acrylonitrile, and 2 parts methacrylamide;i.e., no loader is used. The polymerization is carried out as inExamples 33 to 36. In Example 48, the elastomer latex is prepared bymechanically mixing the latex of Example 47 with a latex prepared by thepolymerization of 90 parts of MMA and 10 parts of vinyl-4-pentenoate,and then stripping out the residual monomer by steam distillation, in aratio which yields 100 parts of the polymer of Example 47 for every 40parts of loading polymer. Finally, for Example 49, the elastomer latexis prepared by polymerizing the mono- TABLE IX Equilibrium lltlodulus(p.s.i.) a

Elong. Tensile Example (percent) (p.s.i.) 200% 250% 300% EXAMPLE 50 Aloader emulsion is prepared as in Examples 1 to 4 from a monomercomposition of 95 parts methyl methacrylate and 5 parts divinylbenzene.A high pressure reactor equipped with a stirrer, heat control system,ethylene pressurization system and two injector pumps is charged with225 g. of the loader emulsion containing 70 g. of polymer solids, 275 g.of deionized water and 30.9 g. of a mixture of g. of ethyl acrylate and4.5 g. of methacrylamide. A solution of 1.0 g. of ammonium persulfate in19 g. of deionized water is prepared and 4.0 g. of this added. Thereactor is then closed, sparged with nitrogen and stirring begun.Ethylene is then added to bring the pressure to 3,900 p.s.i.g. Thereactor is then heated to 80 C. and maintained at this temperaturewithin 3 C. After one hour the remainder of the ethylacrylate-methacrylamide mixture is added in 1 ml. increments, the totaladdition time being 6 hours. The remainder of the ammonium persulfatesolution is also added during this period in 6 equal portions atone-hour intervals. At the end of the monomer and catalyst addition, thereactor is allowed to cool to room temperature, vented, and the emulsionremoved. A total of 700 g. of latex containing 35% solids is produced.

A sample of the emulsion is coagulated by freezing, washed thoroughly toremove impurities, and analyzed. The composition of the rubbery phasefrom this analysis is methacrylamide 1.9%; ethylene 39.0:1.1%; and ethylacrylate 59.l- -l.l%.

A sample of the emulsion is prepared for spinning by adding 6:5 g. of37% aqueous formaldehyde solution per 100 g. of emulsion solids andaging for 48 hours. The latex is then spun as in Examples 1 to 4. Thefiber produced in this manner, without stretch cure, has a tensilestrength of 3000 p.s.i., an elongation of 400% and a running set of 12%from 200% extension.

EXAMPLES 51 TO 53 Using the process described in Examples 1 to 4,rubbery polymers of the following compositions are polymerized in thepresence of 50 parts of a loader prepared from a monomer mixture of 95parts methyl methacrylate and 21 parts divinylbenzene. This loader isalso prepared as described in Examples 1 to 4:

These materials are cast onto an abhesive support(polytetrafiuoroethylene-coated glass), dried at room temperature, andthen cured at 200 C. for five minutes. The films so produced are about12 mils thick, are clear, have good tensile strength, are quite snappy,and are insoluble in common organic solvents such as toluene, ethylenedichloride, perchloroethylene, and tetrahydrofuran.

What is claimed is:

1. A sequential copolymer consisting of:

(A) from 65 to by weight of a loader consisting of solvent-insolublecross-linked polymeric particles comprising at least one vinylidenemonomer, the polymer of which itself in the uncross-linked state has asecond order transition temperature of at least 20 C., and whichcontains no halogen as part of the vinylidene radical, said loaderhaving a particle size of no more than about 1 micron in diameter andprepared by emulsion polymerization using a free radical catalyst and(B) sequentially polymerized on said loader particles from 35 to 90% byweight of an elastomer prepared from a mixture of monomers consistingessentially (l) at least one rubbery C C alkyl ester of acrylic acid ora mixture of one or more of said esters with up to an equal weightpercent of at least one monomer selected from the group consisting ofethylene, propylene, and isobutylene, and

(2) from about 0.5% to 25% by weight of the elastomer mixture of, atleast one monomer having a single unsaturated carbon-to-carbon linkageof sufli-cient reactivity to copolymerize with the elastomer mixture andcontaining at least one radical which is of too low a reactivity tocopolymerize with the elastomeric mixture but which is effective tocross-link the polymer chains formed'from the'elastomer mixture by areaction which is activated separately from the polymerization reaction,

said elastomer mixture being so selected that a polymer produced fromsaid mixture has a second order transition temperature of no more than0".

2. -A sequential copolymer according to claim 1 wherein the elastomermixture contains up to about 20% by weight of the elastomer mixture ofat least one a,;8-monoethylenically unsaturated monomer eifective toincrease the second order transition temperature of the. copolymerproduced from said elastomer mixture.

3. A sequential copolymer according to claim 1 wherein said elastomermixture is selected so that a polymer produced from said mixture has asecond order transition temperature of no more than -20 C.

4. A sequential copolymer according to claim .1 wherein component (B)(1) is butyl acrylate.

5. A sequential copolymer according to claim 4 wherein the elastomermixture contains up to about 20% by weight of the elastomer mixture ofat least one monomer selected from the group consisting of methylmethacrylate, ethyl methacrylate, tertiary-butyl acrylate, styrene,a-methyl styrene, acrylonitrile, vinyl pyridine, vinyl toluene, vinylchloride, vinylidene chloride and methacrylonitrile.

6. A sequential copolymer according to claim 1 wherein component (B)(1)is ethyl acrylate.

7. A sequential copolymer according to claim 1 wherein component (B) (1)is a mixture of ethyl acrylate with up to by weight of ethylene.

8. A sequential copolymer according to claim 1 wherein component (B)( 1)is 2-ethylhexyl acrylate and wherein the elastomer mixture contains upto about 20% by weight of at least one a,,8-mon0ethylenicallyunsaturated monomer effective to increase the second order transitiontemperature of the copolymer produced from said elastomer mixture.

9. A sequential copolymer according to claim 1 wherein the vinylidenemonomer is selected from the group consisting of methyl methacrylate,ethyl methacrylate, tertiary-butyl acrylate, styrene, a-methyl styrene,acrylonitrile, vinyl pyridine and vinyl toluene.

10. A sequential copolymer according to claim 1 wherein the loadercontains a monomer which can undergo a condensation reaction with one ormore complementary monomers in the elastomer mixture.

11. A sequential copolymer consisting of g (A) from to 10% by weight ofa loader consisting of polymeric particles no more than one micron indiameter formed by emulsion polymerization, using a free radicalcatalyst, of a mixture of 1) at least by weight of the loader of atleast one vinylidene monomer which contains no halogen as part of thevinylidene radical with (2) from 1-25% by weight of the loader of atleast one cross-linking'monomer having at least two vinyl groups ofsuflicient reactivity to allow independent copolymerization with thevinylidene monomer, the mixture exclusive of the cross-linking monomerproducing a polymer having a second order transition temperature of atleast 20 C.;

(B) sequentially polymerized on said loader particles from 35-90% byweight of an elastomer prepared from a mixture of monomers consistingessentially of (1) from 7599% by Weight of at least one rubbery' monomerselected from the group consisting of ethyl acrylate, propyl acrylate,butyl acrylate and mixtures of said acrylate esters with up to an equalweight amount of ethylene,

(2) from 0.55% by weight of the elastomer mixture of at least onea,,B-monoethylenically unsaturated monomer copolymerizable with therubbery monomer and containing at least one radical selected from thegroup consisting of hydroxyl, amino, amido, epoxy, ureido and carboxylicacid, and

(3) up to 20% by weight of the elastomer mixture of at least onea,fi-monoethylenically unsaturated monomer effective to increase thesecond order transition temperature of the copolymer produced from saidelastomer mixture; the proportions of monomers in the elastomer mixturebeing selected so that the polymer produced from said mixture has asecond order transition temperature of no more than -20 C.

12. A process for producing an elastomeric sequential copolymercomprising:

(A) in the presence of an eifective amount of a free radical catalystpolymerizing an emulsion of 1) up to about 99% by weight of at least onevinylidene monomer which contains no halogen as part of the vinylideneradical with (2) up to about 25% by weight of at least one diorpoly-functional monomer copolymerizable with the vinylidene monomer andelfective to cross-link the resulting copolymer and being present insufficient amount to make the resulting copolymer substantiallyinsoluble, the polymer of (A) (1) by itself having a second ordertransition temperature of at least 20 0., thereby producing a loaderlatex;

(B) adding to said latex an elastomer mixture of 23 (1) a rubberymonomer selected from the group consisting of at least one rubbery C Caikyl ester of acrylic acid or a mixture of one or more Qof said esterswith up to an equal weight percent of at least one monomer selected fromthe group consisting of ethylene, propylene and isobutylene, and V (2)from about 0.5% to 25% by weight of the elastomer mixture of at leastone monomer having a single unsaturated carbon-to-carbon linkage ofsufiicient reactivity to copolymerize with the rubbery monomer andcontaining at least one radical effective to cross-link the polymerchains formed from the elastomer mixture by a reaction which isactivated separately from the polymerization reaction, the elastomermixture being selected so that a. polymer produced therefrom has asecond order transition temperature of no more than C.; and

(C) polymerizing said elastomer mixture on the loader latex in thepresence of an effective amount of a free radicai catalyst and underconditions designed to minimize the formation of new particles, the:loader latex constituting from about 65 to by weight of the totalcomposition and the elastomer mixture constituting correspondingly fromabout 35-90% by Weight of the total polymer.

13. A process for producing an elastomeric shaped structure comprising:

(A) Preparing a loader latex of a copolymer of (1) from about 75-99% byweight of at least one vinylidene monomer which contains no halogen aspart of the vinylidene radical, said monomer or mixture of monomersproducing a a polymer having a second order transition tempera ture ofat least 20 C., and (2) from 251'% by weight of ,the copolymer of atleast one monome'i having at least two vinyl groilps of 's'ufiicientreactivity to allow indei pendent copolymeri zation with the vinylidenemonomer or monomers; 1B) Polymerizing on saidloaderlatex underconditions which minimize the formation of new particles an elastomermixture of T (1) a rubbery monomer selected from the group consisting ofethyl acrylate, propyl acrylate, hutyl acrylate, and mixtures of saidacrylates with each other and with up to an equal weight percent ofethylene, and (2) from 0.5-5% by weight of the elastomer mixture of atleast one monomer having a sin- 24 gle unsaturated carbon-to-carbonlinkage of sufficient reactivity;;to copolymerize with the rubberymonomer and containing at least onezradical selected from the groupconsisting of amido, amino; carboxyiic acid, hydroxyl, epoxy, uneido andcarbon-to-carbon linkage 0t: too low a reactivity to copolymerize withthe rubbery monomer, and

(3) up to 20% by weight of the elastomer mixture of at least onea,fi-monoethylenically unsaturated monomer etfective to. increase thesecond order transition temperature of the polymer produced from saidelastomer mixture, the polymer produced from said elastomer mixturehaving a second order transition temperature of no more than 0 C.;

(C) Extruding the resulting latex into a coagulating bath through anorifice to produce a coagulated shaped structure, and

(D) Curing the coagulated shaped structure.

.5 14. A process according to claim 13 wherein the curing step iscarried out to partially cure the shaped structure, then the shapedstructure is stretched under tension and, while held in the stretchedcondition, the curing is completed.

15. A sequential copolymer according to claim 1 wherein component (B)(1)is an elastomeric cross-linked c0- polymer of at least one monomerselected from the group consisting of ethyl acrylate, propyl acrylate,butyl acrylate and mixtures thereof with each other, and up to an equalweight percent of ethylene.

16. A fiber prepared from the composition of claim 15. 7 a

17. A film prepared from the composition of claim 15.

References 'Cited UNITED STATES PATENTS r,

Burke a 260-4 Ennor et a1. 260-8 79 SAMUEL H. BLE cH, Primary ExaminerM. J. TULLY, Assistant Examiner US. Cl. X.R.

